Sara Lonardi, MD, Veneto Institute of Oncology, Padova, Italy, reported results from the PEGASUS trial, evaluating the feasibility of liquid biopsy-guided post-surgical and post-adjuvant clinical management of patients with stage IIT4N0/III colon cancer.

Results from this study found liquid biopsy may be use to guide the post-surgical clinical management of patients with colon cancer by reducing unnecessary toxicity and improving the response to standard chemotherapy.

Dr Lonardi concluded, “We do believe that there are not only technical issues in the performance of this strategy, but also biological matters that need to be investigated in the future research,” adding, “we hope that in the future we will have something reliable in understanding more of this tool that is really, really important, but still needs to be fixed.”

These results were first presented at the 2023 European Society for Medical Oncology Annual Congress in Madrid, Spain.

Transcript:

Hi to everybody. I'm Sara Lonardi, chief of Oncology Unit 3 and responsible for the Gastrointestinal Cancer Unit at the Veneto Institute of Padova. I would like to share with you the result of the PEGASUS trial I just now presented here in Madrid at the ESMO 2023 Congress.

The PEGASUS trial was designed to assess the feasibility of a liquid biopsy to guide the choice of the treatment in the adjuvant setting. In other words, we know that patients that have their colon cancer resected may relapse and that clinical factors are of little help in guiding the choice on who will have to receive additional chemotherapy and who doesn’t need it.

The liquid biopsy with a test looking for ctDNA is able to separate prognosis in our population and identify patients with positive minimal residual disease. We used plasma-based genetic and epigenetic test, the Lunar 1.2, to identify positive patients. And then we allocated patients to receive a combination treatment in the case the liquid biopsy was positive, or a monotherapy in the case the liquid biopsy was negative. Then the patient reassessed the ctDNA after the end of the adjuvant phase of the trial and they were escalated or deescalated according to the result of that biopsy.

What we have seen is that the ctDNA was able to nicely separate the prognosis of the patient and it was associated in univariate and multivariate analysis with the time to relapse. In addition, we observed 10 relapses, 10% in our population of 100 patients with negative liquid biopsy and 12 relapses in the 35 patients with the liquid biopsy positive.

What we captures was also that liquid biopsy was able to properly identify relapses that are caused in the liver, but unfortunately not those in the lung and the peritoneum. And so, we do believe that there are not only technical issues in the performance of this strategy, but also biological matters that need to be investigated in the future research.

Follow-up is ongoing. We need to go on because our primary end point was the number of patients relapsing despite a negative liquid biopsy at 24 months, and so we need a longer follow up. But we hope that in the future we will have something reliable in understanding more of this tool that is really, really important, but still needs to be fixed.

Source:

Lonardi S, Pietrantonio F, Tarazona Llavero N, et al. The PEGASUS trial: Post-surgical liquid biopsy-guided treatment of stage III and high-risk stage II colon cancer patients. Presented at the ESMO Annual Congress; October 20-24, 2023; Madrid, Spain. LBA28.